This protocol is based on our preliminary research indicating that red cell membrane lipid peroxidation results in the presence of an extractable fluorescent compound which is presumably derived from the crosslinking of amino groups by dicarbonyl compounds. Such fluorescence has been observed in association with in vitro red cell lipid peroxidation, in rabbits receiving phenylhydrazine, and in patients being treated with the oxidant hemolytic drug diaminodiphenylsulfone. Further studies will be aimed at confirming the relation of this fluorescence to carbonyl compounds by a number of techniques including extraction and identification of such carbonyls from the membrane, incubation of red cells with dicarbonyls, measurement of amino groups in the red cell membrane, and exploring the effects of vitamin E deficiency. The fluorescent technique will be extended to study other human hemolytic processes in which lipid peroxidation may perhaps occur. In addition, the extent to which carbonyl linkage to the red cell membrane might contribute to in vivo hemolysis will be assessed by red cell survival studies and evaluation of red cell filtration.